Celsian - Encyclopedia
Class : Silicates
Subclass : Tectosilicates
Crystal system : Monoclinic
Chemistry : BaAl2Si2O8
Rarity : Uncommon
Celsian, also called celsianite, is a rare term from the feldspar group in which it forms two incomplete series with orthoclase and hyalophane. It was named in honor of the Swedish astronomer and naturalist Anders Celsius. It is an accessory mineral of contact metamorphic rocks, pyrometasomatic manganese deposits and amphibolites. It forms short to elongated prismatic crystals resembling those of orthoclase, which can show Carlsbad, Baveno and Manebach twins, with a maximum size of 2 cm. It is colorless to whitish, straw yellow, sometimes pink when it contains iron oxides.
Main photo : Celsian from Benallt Mine, Rhiw, Wales, United Kingdom © Christophe Boutry
Celsian in the World
Twinning and special crystallizations
Simple twins according to the laws of Manebach, Baveno or Carlsbad are known.
Fakes and treatments
No fake identified for this mineral species.
Hardness : 6 to 6.5
Density : 3.10 to 3.39
Fracture : Irregular
Streak : White
TP : Translucent to transparent
RI : 1.580 to 1.596
Birefringence : 0.014
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None
Solubility : Insoluble
Magnetism : None
Radioactivity : None